It implements load-tracking on a per-sched_entity (currently SCHED_NORMAL, butcould be extended to RT as well) basis. This results in a bottom-upload-computation in which entities contribute to their parents' load, asopposed to the current top-down where the parent averages its children. Inparticular this allows us to correctly migrate load with their accompanyingentities and provides the necessary inputs for intelligent load-balancing andpower-management.

We've been running this internally for some time now and modulo any gremlinsfrom rebasing it, I think things have been shaken out and we're touchingmergeable state.

Special thanks to Namhyung Kim and Peter Zijlstra for comments on the lastround series.